Not a dumb question.
It's something that only happens in the team blocks stat. If a player goes up on their own it's a solo block. If two (or three) players go up and get the block, they are all credited a block regardless who touches the ball. This is a block (assist). When calculating team blocks, you count all the solo blocks and half of all the block assists. So 5 solo blocks and 21 block assists would end up as 15.5 team blocks.
And a block is a stop at the net that directly leads to the point, not just any denial at the net.